Making progress on high rpm
01-12-2012, 03:20 PM
#1
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Year: 1989
Model: Cherokee
Engine: 4.0L I6
Making progress on high rpm
Well, seems like I got it down 250rpm when hot.
Been idling at 1250rpm after it warmed up and now it is at 1000rpm. At cold it is 650rpm. I tightened down all the top manifold bolts. They all were loose. I now have the bottom ones to tighten.
What would be the best angle of attack to get to those?
I just hope that this will fix the high HC count in my emissions so I can pass!
Been idling at 1250rpm after it warmed up and now it is at 1000rpm. At cold it is 650rpm. I tightened down all the top manifold bolts. They all were loose. I now have the bottom ones to tighten.
What would be the best angle of attack to get to those?
I just hope that this will fix the high HC count in my emissions so I can pass!
Last edited by red_dog007; 01-12-2012 at 03:41 PM.
01-12-2012, 04:47 PM
#2
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Year: 1989
Model: Cherokee
Engine: 4.0L I6
Wouldn't unplugging the IAC make a difference?
When I start up without the IAC plugged in, nothing changes. I plug it in, nothing changes.
Im getting less than 14mpg on the highway and this problem is gah...
Hopefully I can get these sensors tested this weekend.
I got under there and got everything tighted up, which everything on the bottom was tight already.
When I start up without the IAC plugged in, nothing changes. I plug it in, nothing changes.
Im getting less than 14mpg on the highway and this problem is gah...
Hopefully I can get these sensors tested this weekend.
I got under there and got everything tighted up, which everything on the bottom was tight already.
01-12-2012, 05:59 PM
#4
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Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Test your TPS on the "engine" side per the following:
RENIX TPS ADJUSTMENT
Before attempting to adjust your TPS be sure the throttle body has been recently cleaned.
It's especially important that the edges of the throttle butterfly are free of any carbon build-up.
IMPORTANT NOTE: Using the positive (red) lead of your ohmmeter, probe the B terminal of the flat 3 wire connector
of the TPS . The letters are embossed on the connector itself.
Touch the black lead of your meter to the negative battery post.
If you see more than 1 ohm of resistance some modifications to the sensor ground harness will be
necessary. The harness repair must be performed before proceeding.
I can provide an instruction sheet for that if needed.
MANUAL TRANSMISSION:
RENIX manual transmission equipped XJs have a three-wire TPS mounted on the throttle body.
This manual transmission vehicle TPS provides data input to the ECU. The manual transmission
TPS has three wires in the connector and they're clearly embossed with the letters A,B, and C.
Wire "A" is positive.
Wire "B" is ground.
Key ON, measure voltage from "A" positive to "B" ground by back-probing the connectors..
Note the voltage reading--this is your REFERENCE voltage.
Key ON, back-probe the connector at wires "B" and "C". Measure the voltage. This is your
OUTPUT voltage.
Your OUTPUT voltage needs to be seventeen percent of your REFERENCE voltage. For
example: 4.82 volts X .17=.82 volts. Adjust the TPS until you have achieved this percentage. If
you can't achieve the correct output voltage replace the TPS and start over.
AUTOMATIC TRANSMISSION:
RENIX automatic transmission equipped XJs have a TPS with two connectors. There is a flat three-
wire connector, same as the manual transmission vehicles have, and it is tested the same as the
manual transmission equipped vehicles--FOR ENGINE MANAGEMENT RELATED ISSUES.
However, the automatic TPS also has a square four-wire connector clearly embossed with the letters
A,B,C, and D. It only uses three wires and provides information to the Transmission Control Module.
Key ON, measure voltage between "A" positive and "D" ground. Note the voltage. This is your
REFERENCE voltage.
Back-probe the connector at wires "B" and "D". Measure the voltage. This is your OUTPUT
voltage. Your OUTPUT voltage needs to be eighty-three percent of your REFERENCE voltage.
For example 4.8 volts X .83=3.98 volts. Adjust the TPS until you have achieved this percentage.
If you can't, replace the TPS and start over.
So, if you have an automatic equipped XJ your TPS has two sides--one side feeds the ECU, and
the other side feeds the TCU. If you have TRANSMISSION issues check the four-wire
connector side of the TPS. If you have ENGINE issues check the three-wire connector side of
the TPS.
For those with a MANUAL TRANSMISSION--the TPS for the manual transmission XJs is
stupid expensive. You can substitute the automatic transmission TPS which is reasonably priced.
Revised 11-28-2011
RENIX TPS ADJUSTMENT
Before attempting to adjust your TPS be sure the throttle body has been recently cleaned.
It's especially important that the edges of the throttle butterfly are free of any carbon build-up.
IMPORTANT NOTE: Using the positive (red) lead of your ohmmeter, probe the B terminal of the flat 3 wire connector
of the TPS . The letters are embossed on the connector itself.
Touch the black lead of your meter to the negative battery post.
If you see more than 1 ohm of resistance some modifications to the sensor ground harness will be
necessary. The harness repair must be performed before proceeding.
I can provide an instruction sheet for that if needed.
MANUAL TRANSMISSION:
RENIX manual transmission equipped XJs have a three-wire TPS mounted on the throttle body.
This manual transmission vehicle TPS provides data input to the ECU. The manual transmission
TPS has three wires in the connector and they're clearly embossed with the letters A,B, and C.
Wire "A" is positive.
Wire "B" is ground.
Key ON, measure voltage from "A" positive to "B" ground by back-probing the connectors..
Note the voltage reading--this is your REFERENCE voltage.
Key ON, back-probe the connector at wires "B" and "C". Measure the voltage. This is your
OUTPUT voltage.
Your OUTPUT voltage needs to be seventeen percent of your REFERENCE voltage. For
example: 4.82 volts X .17=.82 volts. Adjust the TPS until you have achieved this percentage. If
you can't achieve the correct output voltage replace the TPS and start over.
AUTOMATIC TRANSMISSION:
RENIX automatic transmission equipped XJs have a TPS with two connectors. There is a flat three-
wire connector, same as the manual transmission vehicles have, and it is tested the same as the
manual transmission equipped vehicles--FOR ENGINE MANAGEMENT RELATED ISSUES.
However, the automatic TPS also has a square four-wire connector clearly embossed with the letters
A,B,C, and D. It only uses three wires and provides information to the Transmission Control Module.
Key ON, measure voltage between "A" positive and "D" ground. Note the voltage. This is your
REFERENCE voltage.
Back-probe the connector at wires "B" and "D". Measure the voltage. This is your OUTPUT
voltage. Your OUTPUT voltage needs to be eighty-three percent of your REFERENCE voltage.
For example 4.8 volts X .83=3.98 volts. Adjust the TPS until you have achieved this percentage.
If you can't, replace the TPS and start over.
So, if you have an automatic equipped XJ your TPS has two sides--one side feeds the ECU, and
the other side feeds the TCU. If you have TRANSMISSION issues check the four-wire
connector side of the TPS. If you have ENGINE issues check the three-wire connector side of
the TPS.
For those with a MANUAL TRANSMISSION--the TPS for the manual transmission XJs is
stupid expensive. You can substitute the automatic transmission TPS which is reasonably priced.
Revised 11-28-2011
01-12-2012, 07:43 PM
#5
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Location: Los Angeles
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Year: 1996
Model: Cherokee
Engine: 4.0 H.O.
Well, seems like I got it down 250rpm when hot.
Been idling at 1250rpm after it warmed up and now it is at 1000rpm. At cold it is 650rpm. I tightened down all the top manifold bolts. They all were loose. I now have the bottom ones to tighten.
What would be the best angle of attack to get to those?
I just hope that this will fix the high HC count in my emissions so I can pass!
Been idling at 1250rpm after it warmed up and now it is at 1000rpm. At cold it is 650rpm. I tightened down all the top manifold bolts. They all were loose. I now have the bottom ones to tighten.
What would be the best angle of attack to get to those?
I just hope that this will fix the high HC count in my emissions so I can pass!
01-12-2012, 10:26 PM
#6
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Location: Nor-Cal Coast
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Year: 90,84
Model: Cherokee
Engine: 4.0,2.5
You pull the air cleaner. then for that very back one I use allot of extensions with a universal. Manifolds, especially exhaust can crack. You never want the bolts un-even. I'd work from the middle out three times, doing both upper and lower.
One lower bolt toward the rear can be a little tough. Be sure to check the vacuum line to the MAP sensor. That Map and the 02 sensor set your mixture, HC is gas.
One lower bolt toward the rear can be a little tough. Be sure to check the vacuum line to the MAP sensor. That Map and the 02 sensor set your mixture, HC is gas.
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